A technique was described using mice which employed a stainless steel skin depot to study the percutaneous absorption of volatile substances. Previously employed systems were not effective in trapping the vaporized portion of highly volatile test materials, and often resulted in falsely elevated estimates of dermal absorption. The skin depot described contained activated charcoal or similar absorbent material which captured the vaporized portion of test chemicals for analysis. The skin depot was tested for its ability to quantitatively capture the evaporated portion of volatile test materials, its ability to adhere to hairless-mouse skin, and its ability to restrict the contact area of the test solvent to the circumscribed skin site. To evaluate ability to contain the test material at the circumscribed site, 5 to 20 microliters of acetone (67641) colored with methylene-blue were placed in the depots. After 15 minutes, the depots were removed and sites were visually inspected for color. Results of this study indicated that there was no leakage of solvent beyond the treatment site. In a second group of experiments, carbon-14 labelled benzene (71432) was instilled into skin depots attached to mice which had just been killed. The mice were placed in a metabolism cage and after 4 hours any leakage of radioactivity was measured. Results indicated that under the test conditions, the depots were capable of absorbing all of the volatilized material. To determine the maximum time for absorption of test substances, 5 microliters of labelled benzene were instilled into depots glued to anesthetized hairless mice. The depots were removed and the radioactivity remaining within was determined at intervals up to 2.5 hours. Results of this study indicated that absorption was maximal after 1.5 minutes and remained unchanged up to 2.5 hours.